1. Field of the Invention
The present invention generally relates to optical equipment assemblies and techniques, and more particularly to disc media metrology.
2. Description of the Related Art
A form of an information storage and retrieval device is a hard disc drive (xe2x80x9cdisc drivexe2x80x9d). A disc drive is conventionally used for information storage and retrieval with computers, data recorders, redundant arrays of independent discs (RAIDs), multi-media recorders and the like. A disc drive comprises one or more disc media.
Each disc media comprises a substrate upon which materials are deposited to provide a magnetically sensitive surface. In forming the magnetically sensitive surface, a servo pattern or more particularly servo pattern media, may be formed on such substrate. A servo pattern media conventionally is a pattern of raised features, such as posts or columns. In a servo pattern, position error signal (PES) marks may be formed. Such PES marks conventionally are a pair of contiguous or inter connected posts. In addition to such servo pattern media, another form of pattern media that may be formed on a substrate is bit pattern media. A bit pattern or bit pattern media is an arrangement of posts or columns for storing bits of information.
As disc media storage requirements increase, namely, density is enhanced, topographic features whether for servo pattern media, bit pattern media or other media become smaller. For example, PES marks in bit patterns may be formed below 500 nanometers in lateral dimension. Moreover, as such posts become smaller in lateral dimension, spacing between posts also decreases. Thus, viewing such posts, as well as regions between posts, by conventional means is not practical. For example, a conventional interference based microscope uses a monochromatic light source of approximately 550 nanometers. Because the wavelength of the light source is larger than lateral dimension of the bit pattern elements themselves, a conventional interference based microscope is not sufficient for detailed resolution of topographic information associated with such pattern media.
Accordingly, an atomic force microscope (AFM) may be used to scan a disc media surface. An AFM scans not optically, but by physical touch using a contact probe. However, a difficulty arises in locating patterns for identifying a correct contact starting position for an AFM scan. Conventionally, a technician uses an interference-based microscope to locate a pattern; however, as mentioned above owing to resolution limitations of such conventional interference-based microscopes placement of probe tip is problematic. It should be appreciated that an AFM probe tip may be as narrow as 1 nanometer.
Not all servo pattern media uses topographic features. Some servo patterns are completely magnetically written. Conventional magnetically written servo patterns do not have topographic features, and thus rather than relying on spacing loss to generate a differential signal as in topographically patterned surfaces, magnetically written patterns rely on magnetic domain switching. Such magnetically written patterns are not detectable with topography. However, some servo patterns are a combination of topographic features and detectable magnetic information.
Accordingly, it would be desirable to provide for detection of servo or other patterns or features whether produced topographically or magnetically or both. More particularly, it would be desirable to provide for detection of servo patterns for determining a starting position for an AFM scan in order to obtain nano-scale image or other information.
The present invention generally provides method and apparatus for detecting a scanning a media. More particularly, an aspect of the present invention comprises a stage, a spindle configured to support the media, a first linear actuator connected to the stage, a second linear actuator connected to the stage, a polarization detector connected to the first linear actuator and positionable to scan the media, and an atomic force microscope connected to the second linear actuator and positionable to scan the media. The polarization detector is configured to provide optical energy incident on the media and to detect change in polarization of the optical energy reflected from the media to provide magnetic imagery of the media. The polarization detector and the atomic force microscope indexed to the spindle.
Another aspect of the present invention is a method for scanning a media. A polarization detector, an atomic force microscope, a platform, a first linear actuator, a second linear, and a spindle are provided. The spindle is centrally located with respect to the platform. The first linear actuator is coupled to the platform and the polarization detector, and the second linear actuator is coupled to the platform and the atomic force microscope. A servo pattern magnetically written to the media is detected with the polarization detector. The atomic force microscope is positioned in response to the servo pattern for the scanning of the media with the atomic force microscope.
Another aspect of the present invention is an apparatus for scanning a media comprising means for supporting and rotating the media; means for detecting polarization for providing a magnetic image of the media indexed to the means for supporting and rotating the media; means for probing the media for providing a topographic image indexed to the means for supporting and rotating the media; and means for providing a common rotatable platform for the means for detecting polarization and the means for probing.